Manfred

I thought I'd seen posts about this before but I can't seem to find the thread. My front A/C works well (although I now have the problem where there is a problem with the sensor circuit and it only blows cold when the ac switch is all the way over to the left on 65) but the rear ac blows warm. The fan comes on and works fine.

If I remember correctly the compressor is the same but there is a different evaporator in the rear? Is there a known common problem that causes the front AC to be cold and the rear ac to be warm? Bad expansion valve?

Thanks
Dan
(91GT, 5sp).

p.s. would not be disappointed in replies in the form of links to previous posts if this has already been hashed out somewhere else...

JPTL

Bad expansion valve could be the culprit. I say this not because I'm an AC expert, but because my rear e-valve was almost completely crudded up, but my front looked good. Both were originals, I believe.
An AC guy can correct me if I'm wrong, but I believe that when an e-valve gets crudded up, the lack of circulation can cause abnormal amounts of pressure on o-rings and can cause premature freon leakage, particularly in at those seals closest to the valve. My leaks were all around the back e-valve.
These valves need to get frequent circulation of freon or else they'll start to get a crud build up over time. If the rear system is hardly used like w/most of our cars, everything stays stagnant back there and seals dry and e-valves are stagnant & get nasty (the plaque in the arteries > high blood pressure > heart attack is a good analogy).
The rear e-valve is easy to get to & replace. Not nearly the pain that the front is.
Obviously your system will be open when you do an e-valve replacement, so do front & back as well as an o-ring replacement WYIT.

Jim bailey - 928 International

Under the passenger seat the A/C lines pass through the floor pan there is a connection there with a solenoid valve 928 615 201 01 . That valve opens and closes when you use the rear A/C unit. That should be checked for function. The supply line for pressurized refrigerant is a simple T near the firewall and the solenoid valve under the seat allows the rear evaporater to SHARE the freon. IF the rear expansion valve were blocked (not that likely) then the system just operates as a regular no rear air unit with no extra pressure.

JPTL

Well there you have it

SteveG

Jim: How do I check that s-valve for function? Does the system have be dumped to replace it? I was looking at the tubing on the floor and didn't really pay much attention to it. I don't really need the rear air and the front is nice and cold; I hesitate to mess w/it for fear of knocking some crud loose which then goes into the expansion valve.

killav

Not trying to be a smart *** at all here, but try and turn the dial on the center console (next to the rear fan controller) the other way. It might be on full warm.

Jim bailey - 928 International

First check to see that it get powered when you turn the switch (test light /multimeter) . Then see if you can feel/hear it moving as you apply 12 power and release it. Looks like a brown and a blue wire to the solenoid switch , brown is ground.

SteveG

No offense taken, but both of us who have the problem have said we have cold in front, (and Manfred says as much) we have center slider to the left and rear fan on and the intesity dial to max, right Manfred? Granted humidity here is high, but my system puts water vapor on the inside of windshield above the dash vents, blower not even on high.

Jim: so I should find wires under the carpet to the switch or is this in the rear console? Hmmmm. Should be easy. Thanks.

Manfred

Yes, my front A/C blows very cold, center slider all the way to the left, rear fan intensity on max but warm air in back. Thanks for the tip on the solenoid Jim. +1 on Steve's question--the solenoid is under the carpet under the passenger seat? Does the seat need to be removed (just got my 1st 928 last month so I'm still learning where all the parts are hidden)?

Dan

Jim bailey - 928 International

Yes under the passenger seat ...

Alan

Do as Jim says then check the line going into & out of the solenoid valve. If you have flow it should get cold downstream - no flow may be the rear expansion valve blocked or partly blocked... If only partly you may fell the line flowing and cooling a bit. If no flow at all then it may also be the solenoid valve not opening.

Yes you have to remove the seat

If the solenoid power doesn't switch make sure the flow potentiometer is connected correctly in the console - if the connections fall off the back you won't get cooling.



Alan

Manfred

Thanks Alan, guess the passenger seat is coming out in the distant future--it's down my list a little right now as my gas smell continues to be my main priority...
Dan

dr bob

You can usually raise the pass seat up all the way and reach a hand underneath to feel the soleniod valve. Have someone cycle the rear AC and you should be able to feel the valve click open and closed. If no clicking, then verify that the switch and potentiometer in the console are connected. Sometimes other console work dislodges the connections.

Manfred

I could see how work in the console could have disrupted the connections--some rather serious aftermarket stereo work was done at some point. I am presuming the potentiometer is directly behind the rheostat ****, what switch are you referring to? The one that controls the fan speed (this one should be working for me as the fan does come on)? or is there another switch that you are referring to.

dr bob

The fan speed switch. Fan must be on .and. temp **** not at minimum to cause the solenoid to actuate.